Technically, a bot can connect to your Discord server and compare users ID and groups.
So, all information is already "public".
GDPR does not apply to a person (assuming the Discord management is not considered an "organization", I didn't check the GDPR definition and all its local adaptations),
Local legislation does apply though, and sharing personal information without consent is illegal in several EU countries.
In theory, you should inform any player of the implications before they register (if they process, they consent).
On the development side, I would start by publishing a list of { discord_id, name, pledge_level } on an API.
- The bot is just sugar on top of it and can be open sourced.
- If someone wants to code his/her own bot, he/she can do so too.
@DarkHorizon from an organization perspective, users may not like to give their info to an external Discord, be it the Discord community one.
Regards,
Shadow